<!DOCTYPE html>
<html>
<head>
    <title>My first three.js app</title>
    <style>
        body { margin: 0; }
        canvas { display: block; }
    </style>
</head>
<body>

<script type="module">
    import * as THREE from 'https://threejsfundamentals.org/threejs/resources/threejs/r125/build/three.module.js';
    var scene = new THREE.Scene();
    var camera = new THREE.PerspectiveCamera(75, window.innerWidth/window.innerHeight, 0.1, 1000);

    var renderer = new THREE.WebGLRenderer();
    renderer.setSize(window.innerWidth, window.innerHeight);
    document.body.appendChild(renderer.domElement);

    var radius = 5;
    var segments = 64;
    var thetaStart = 0;
    var thetaLength = Math.PI / 3; // 1/6 of a circle

    // Create a circle geometry
    var geometry = new THREE.CircleGeometry(radius, segments, thetaStart, thetaLength);

    var material = new THREE.MeshBasicMaterial({
        color: 0xff0000, // red
        side: THREE.DoubleSide,
        transparent: true,
        opacity: 0.5
    });

    var radar = new THREE.Mesh(geometry, material);
    scene.add(radar);

    camera.position.z = 10;

    function animate() {
        requestAnimationFrame(animate);

        radar.rotation.z += 0.01;

        renderer.render(scene, camera);
    }

    animate();
</script>
</body>
</html>
